Weakening Pd─O Bonds by an Amorphous Pd Layer to Promote Electrocatalysis.

Construction of core-shell structured electrocatalysts with a thin noble metal shell is an effective strategy for lowering the usage of the noble metal and improving electrocatalytic properties because of the structure-induced geometric and electronic effects. Here, the synthesis of a novel core-shell structured nanocatalyst consisting of a thin amorphous Pd shell and a crystalline PdCu core and its significantly improved electrocatalytic properties for both formic acid oxidation and oxygen reduction reactions are shown. The electrocatalyst exhibits 4.1 times higher catalytic peak current density and better stability in the formic acid oxidation compared to both a PdCu nanoalloy catalyst and a Commercial Pd-C catalyst. An excellent electrocatalytic performance of the core-shell nanocatalyst is also observed in the oxygen reduction reaction. Computational calculation results reveal that tuning of the electronic state of Pd by the amorphous shell and the Cu in the PdCu core weaken the binding strength of surface Pd─O bonds, leading to a bond elongation to facilitate bond breaking. As a result, the electrocatalytic activity in both formic acid oxidation and oxygen reduction reactions is enhanced.